Split-ring resonators (SRR) have been widely used for applications in electromagnetic spectrum spanning from microwave to photonic frequencies. SRR structure defines a basic inductance-capacitance (LC) resonator electrically. The resonant frequency of the resonator is determined with the geometry of the structure. The structures whose dimensions are measured by millimeter and centimeters are generally used for applications in microwave frequency. Structures in micrometer-scale are used for terahertz frequencies, while smaller structures in nanometer-scale work in infrared and the visible light spectrum. When SRR structures are excited appropriately, the magnetic permeability becomes negative within the vicinity of the resonant frequency of the structure. This property is used for developing extraordinary properties such as negative index of refraction.
Unlike other passive resonator tanks, SRR structures can exhibit sharp resonant behavior with quality factor 1000 and above in microwave frequencies. Thus, the changes in resonant frequency of SRR structures can be used as a very effective sensing mechanism. The strain sensors working on this basis have been demonstrated in the literature [1-6]. The changes in SRR geometry due to strain change the resonant frequency of the structure, and this change is measured. Further, the resonant frequency is sensitive to change in dielectric constant of the medium in which the structure is present. This property has also been used for microfluidic applications. The geometry of the structure does not change in these applications, however the changes in dielectric properties of the medium in which it is present result in changes in the effective capacitance of the SRR structure, therefore the resonant frequency of the structure shifts. Biosensors using this mechanism have also been developed. Biomolecules binding on the surface of SRR structures alters the dielectric constant of the structures. SRR structures used with microstrip lines have been demonstrated for applications of hormone and antigen detection. Similar structures have been used for measuring biotin-streptavidin interaction and DNA hybridization.
External antennas are used for electrical excitation of SRR structures in the state of the art. The alignment of these antennas imposes an important limitation to realize portable sensors. In addition, large external antennas are not suitable for integration with electronic chips.
The transmission (s21) characteristic (s21 spectrum) of SRR structures demonstrated in the current technique exhibits a sharp dip at resonance. The shift of this dip frequency can be measured with measurement equipment such as vector network analyzers. However, it is not advantageous to use the sensors exhibiting this electrical property as part of oscillators by integrating with electronic circuits.
Korean Patent Document No. KR20140079094 (A), an application known in the state of the art, discloses a resonator, the electrical parameters of which change under interaction with biomolecules and wherein the said change is measured with a measurement method used with the resonator. The measurement method, which requires direct electrical connection to the resonator structure is different from the inventive system. In the inventive biosensor, direct electrical connection to the resonator structure is not required; this structure is excited with electromagnetic waves. The antennas integrated to the resonator for excitation can be used with different measurement methods.
European Patent Document No. EP1912062 (A1), an application known in the state of the art, discloses a structure the electrical capacitance value of which can change. The said structure is comprised of electrodes defined on a dielectric substrate. The electrodes are coated with biomolecules, and the electrical capacitance of the structure changes due to interaction between biomolecules. The change in capacitance is detected using an electronic circuit which is used together with the electrodes. The said disclosed structures are different from the inventive biosensor in terms of both function and structure. Contrary to EP1911206 (A1) disclosing a capacitor, the inventive system suggests a new resonator structure. With the inventive BioSRR method, disclosed is a new resonator operating in microwave band, the surface of which can be coated with biomolecules, integrated with an antenna is disclosed. The said resonator is excited by means of the integrated antennas, and the resonance frequency shifts can be measured.
In the article published as “Displacement Sensor Based on Diamond-Shaped Tapered Split Ring Resonator”, IEEE SENSORS JOURNAL, VOL. 13, NO. 4, APRIL 2013, blown in the state of the art, a sensor structure has been developed for measuring displacement information on the position and the structure. The structure is defined in a coplanar waveguide for the measurements. The electrical characteristics of the structure are measured by means of the said waveguide. The sensor disclosed in this article is different from the inventive BioSRR in terms of measurement method and the structure.
U.S. Pat. No. 7,964,144 (B1), a patent known in the state of the art, discloses a structure comprised of a pair of electrode structure defined on a substrate and AIN base structure defined in the middle of the electrodes. The electrodes are used to form a horizontal surface acoustic wave and to collect the formed wave. The said method is used for different applications in the field, and it is different from the resonator defined with the inventive BioSRR.
In the article published as “Compact size highly directive antennas based on the SRR metamaterial medium”, New Journal of Physics, 7 (2005) 223 in the state of the art, split-ring resonator structures defined on FR4 substrate are disclosed. The frequency responses of these structures are measured by means of external monopole and horn antennas. Furthermore, these structures are placed inside the antennas, and directed wave propagation is achieved. The application disclosed in this article is completely different from the inventive BioSRR. Furthermore, the method used to excite the resonator structures in BioSRR method is based on defining the resonator and the antenna on a single substrate in an integrated manner. These antennas and the structure are excited with hybrid Tem mode wave. On the other hand, resonator and antenna structures in the BioSRR method are defined on top of a dielectric substrate that is attached to a metal backplate. The presence of this backplate results in the transmission (s21) and reflection (s11) characteristics observed in this article.
The structure disclosed in the article published as “Efficient, Metamaterial-Inspired Loop-Monopole Antenna with Shaped Radiation Pattern”, 2012 Loughborough Antennas & Propagation Conference in the state of the art is a new antenna. The disclosed antenna is electrically loaded with a split-ring resonator, and improvements in transmission/reflection characteristic of the antenna are achieved. The application fields of the structure disclosed in this article and the inventive BioSRR structure are different from each other. BioSRR method does not suggest a new antenna structure. A pair of monopole patch antennas integrated to the resonator structure is used for measuring the resonator characteristic. Split-ring resonator is used as a sensor structure in BioSRR. Furthermore, resonator and antenna structures in the BioSRR method are defined on top of a dielectric substrate that is attached to a metal backplate. The presence of this backplate results in the transmission (s21) and reflection (s11) characteristics observed in this article.
In the article published as “Enhanced transmission of electromagnetic waves through split-ring resonator-shaped apertures”, Journal of Nanophotonics 051812-1 Vol. 5, 2011 known in the state of the art, split-ring resonators are integrated to the waveguides, and used to increase the electromagnetic permeability of the guide. In this application, the electromagnetic wave propagates along with the normal of the resonator structure, so the incidence angle is 90°. The device disclosed in this article is completely different from the inventive BioSRR in terms of application structure and function. In BioSRR method, it is the antenna pair exciting the resonator, not the waveguide. The electromagnetic wave propagates perpendicular to the normal of the resonator, so the incidence angle is 0°.
United States Patent Application No. US20110152725A1, an application known in the state of the art, discloses a structure comprised of planar coil and split-ring resonators suggested for biological applications. These structures are especially used for displacement measurement. External antennas are used for the measurements. The said measurement method is different from the method of using an integrated pair of antennas with the resonator suggested in BioSRR. Furthermore, the resonator and antenna structures in the BioSRR method are defined on top of a dielectric substrate that is attached to a metal backplate. The presence of this backplate results in the transmission (s21) and reflection (s11) characteristics observed in this article.